1. Field of the Invention
The present invention relates to a transmission wheel pressurizing apparatus, in which a pressurizing apparatus of applying to two transmission wheels of a continuously variable speed drive of a constant horsepower transmission type used for industrial machinery such as machine tools, vehicles, motors and the like, wherein both functions of constant horsepower type press control and automatic aligning are assured while stabilizing frictional transmission, and as a result, high-speed response controllability and high efficiency operation are achieved to realize a continuously variable speed drive of high quality and high respectability.
2. Description of the Prior Art
A transmission wheel pressurizing apparatus is well known from Japanese Patent Application Laid-Open No. Hei. 9-217819 (applicant: Van Doorne's Transmissie b. v.). This is a pressurizing apparatus in which out of two disks, a sliding disk itself constitutes, as a pressurizing apparatus, a part of a hydraulically driven piston cylinder, and the disk is directly pressed and slidably moved to change the radius of a transmission wheel and a transmission member to change speed. The direct pressurizing apparatus using oil pressure includes two merits, (1) a suitable pressurizing force from high to low is obtained in a narrow space, and (2) a bearing as a consumable article is not necessary. However, hydraulic control has the following two fatal and decisive defects of a variable speed drive, (1) since the oil pressure has no elasticity, when the transmission wheel is directly pressed, elasticity absorption and automatic aligning function cannot be secured with respect to shocks, errors or the like, and (2) the hydraulic medium is directly affected by delay in operation, oil leakage, centrifugal force or the like so that most fundamental transmission operation is always unstable.
Horsepower P normally transmitted to a load apparatus by a transmission wheel 1 is represented by the following equation in a relation between the number of revolutions N and the torque T: EQU P[W]=1,027.times.N[rpm].times.T[kgm]
Accordingly, it is necessary for transmitting fixed horsepower P0 to reduce the torque T of a transmission member when the number of revolutions N increases, and to increase the torque T when the number of revolutions N reduces conversely.
In the aforementioned related art, an elastic means such as a spring is juxtaposed on the disk of a follower transmission wheel. A compression pressurizing force supplied to a sliding disk by the elastic means increases in pressure as a high-speed rotational state assumes, while it decreases in pressure as a low speed rotational state assumes. Originally, in the constant horsepower transmission type speed variator, despite that an applied pressurizing force need be increased as the lower speed rotation assumes, the direction of the compression pressurizing force of the elastic means is exactly reverse. Accordingly, in the pressurizing apparatus of elastic means of this kind, constant horsepower transmission cannot be realized in principle.
According to the present invention, when the transmission wheel is press controlled, a pressurizing force and an elastic force are always simultaneously applied to one of two transmission wheels, and only the pressurizing force is always applied to the other. The pressurizing system of the former for always simultaneously applying the pressurizing force and the elastic force together is proposed as leading common measures. First, this does not depend on the direct pressurizing system using oil pressure; the former employs an indirect pressurizing system using an elastic member for the constant horsepower type pressurizing control while the latter employs a sliding device free from disturbance of the value of a pressed pressurizing force due to the elasticity, unstable pressure or the like, for realization of intended object. Secondly, a huge elastic member having an extremely large elastic force is indispensable, and problems created by it such as a problem of a centrifugal force of respective members and apparatuses, of an installation in a narrow space, and of an operatabilities such as assembly and disassembly are to be solved.
As the first measures, a normal elastic member of positive characteristic which increases a pressurizing force as a displacement amount of compression increases is used. A compression device is combined with the elastic device with pressurizing forces superposed in series with each other whereby the pressurizing force applied to the transmission wheel causes the relation with the number of revolutions of the transmission wheel to be in inverse proportion to each other to realize the negatively inclined pressurizing characteristic to assure the pressurizing control of fixed horsepower transmission and assure the simultaneous and constant application of not only the pressurizing force but also the elastic force to the transmission wheel and the elastic device.
As the second measures, the elastic device and the compression device are combined to secure the operative connection between the transmission wheel and the elastic device to thereby allow them the constant delivery and reception of not only the variable press control pressurizing force but also the elastic force of the elastic device for the transmission wheel.
For operating a large elastic, there is required a compression device providing a large pressurizing force, therefore. As the third measures, the compression device released from bad influence such as a centrifugal force resulting from rotation, and the periphery of the transmission wheel arranged in the narrow space is kept from cumbersome operating apparatuses as much as possible to constitute a simple control mechanism so as to always supply normal variable press control.
As the fourth measures, in the continuously variable speed drive, it is required that a first part for performing the desired shaft torque transmission and a second part for performing the speed change transmission of the accurate and desired number of revolutions need to function simultaneously; therefore, the first part and the second part are allotted to a first driven transmission wheel and a second driving transmission wheel, respectively, and a first pressurizing apparatus for performing the first part to the first driven wheel and a second pressurizing apparatus for performing the second part to the second driving wheel are separately applied to whereby the constant horsepower pressurizing transmission function and the number of revolutions variable speed function are accomplished in association with each other and simultaneously, as a consequence of which the high-speed response and the high efficiency of variable speed control section are secured.
As the fifth measures, in realizing the aforementioned first to fourth problems, it is actually indispensable upon mounting how the presence of the elastic member of maximum dimension and maximum weight is miniaturized to enhance the simplicity in handling. The elastic member having a large spring constant produces a deformation and deterioration phenomenon early, and therefore, there is provided a transmission wheel pressurizing apparatus which enhances a small storing property for one or more elastic members having a small spring constant in order to avoid the deterioration of a compression pressurizing force, and a workability of assembly and disassembly of a variable speed drive itself.
As the sixth measures, a maximum elastic material is finely divided into a number of elastic members, and there is constituted into inverse proportional pressurizing characteristics of small and acute inclination having negative inclination wide in dynamic range in which the number of revolutions/pressurizing force characteristics applied to the transmission wheel by the pressurizing apparatus is hard to be secured by a single elastic member, consequentially, there is provided a transmission wheel pressurizing apparatus which realizes high efficient transmission in a variable speed transmission section.